Scaffold tender

ABSTRACT

A scaffold tender for suspending a transverse work platform across the underside of highway bridges or the like. The scaffold tender comprises a wheeled framework supported on the bridge deck. A plurality of longitudinally spaced supports are mounted at each side of the framework, each support being selectively retractable in order to clear vertical abutments during movement of the framework along the bridge. The work platform is alternately suspended from one or more of the extended supports during movement of the scaffold tender. The method of traversing the bridge involves the alternate use of the supports and the movement of each support between a retracted position and an extended position as required to clear obstructions encountered in the path of movement of the framework.

I United States Patent [72] Inventors Jamel H. Blake 3,145,801 8/1964Callahan 182/63 1520 E. Capital Expreaway#220, San 3,456,756 7/1969Price 182/63 Jose, Calif. 95121; 3,524,520 8/ 1970 Tidwell 182/36 mumBarber 6800 Enterprise Road Primary Examinr-Reinaldo MachadoAttorney-Wells St. John & Roberts [211 App]. No. 27,867 [22] Filed Apr.13, 1970 [45] Patented Sept. 28, 1971 7 ABSTRACT: A scaffold tender forsuspending a transverse I 54] SCAFFOLD TENDER work platform across theunderside of highway bridges or the like. The scaffold tender comprisesa wheeled framework sup- 8 Claims, 12 Drawing Fig.

ported on the bridge deck. A plurality of longitudinally spaced U-S.supports are mounted at each side of the framework each 132/37, 182/142support being selectively retractable in order to clear vertical m 83/10 abutments during movement of the framework along the [50] Field ofSearch 182/63, 36, bridge The work l tf is alternately Suspended f one150 or more of the extended supports during movement of the 56 R t CMscaffold tender. The method of traversing the bridge involves 1 e thealternate use of the supports and the movement of each UNITED STATESPATENTS support between a retracted position and an extended position2,669,490 2/1954 Kaufman 182/63 as required to clear obstructionsencountered in the path of 2,639,950 5/1953 Wheeler 182/37 movement ofthe framework.

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II II H as PATENTED SEP28 I971 SHEET 1 BF 4 INVENTOR. Jun. H. BIO! Rich5.

PATENTEUSP28|9I| 3508.670

sum 2 [IF 4 INVENTOR. James H. Blake Richard E. Barber scmou) TENDERBACKGROUND OF THIS INVENTION In the construction of bridges forhighwayor other use, concrete formsare utilized on the underside of the bridgedeck and these forms must be stripped after pouring of the concretedeck. The bridge structure usually includes supporting piers. Inaddition, substantial bridge arches are conventionally supported by asteel superstructure, suspension cables or the like, which extendupwardly from the deck at each side of the bridge. These elementscomprise vertical abutments encountered in the path of movement of anyoverhanging apparatus mounted onthe bridge deck.

Because of the obstructions encountered by a movable scaffold tenderonthe bridge deck, it has been conventional to construct stationaryscafi'olding completely across such a bridge for purposes of formremoval and painting. For safety, it is generally required that nets besuspended across the arch. The construction of such scaffolds and theutilization of nets imposes considerable expense on such a project, mostof which can be eliminated if a scaflold could be moved across thebridge.

Prior patent disclosures have shown mobile scafi'old supports designedto clear the piers of bridges. Examples are shown in U.S. Pats. Nos.2,669,490, 3,035,659 and 3,145,801. However, these patent disclosuresindicate no effort to provide for clearance of vertical obstructionsabove the poured deck and would only be useful on bridges supportedentirely by piers and clear of all superstructures.

SUMMARY OF THE INVENTION The scaffold tender disclosed below comprises arigid framework having an effective width less than the width of thebridge deck and movably carried by wheels in engagement with the uppersurface of the bridge deck in order that the framework may belongitudinally moved along the Means are provided on the framework forselectively fixing the framework relative to the bridge deck duringstripping of forms; painting of the bridge underside, or similar workingoperations. A plurality of transverse supports are mounted to theframework at longitudinally spaced positions at both sides of theframework. Each support is independently mounted for selective movementrelative to the framework between a retracted position located withinthe outside boundaries of the bridge deck to permit the framework toclear vertical obstructions and an extended position with one end of thesupport located outward of these boundaries to permit suspension of aplatform structure from the extended end.

According to the method of this invention, a working platform beneaththe deck of a bridge is supported by suspending the ends of the platformfrom a pair of longitudinally spaced and horizontally retractablesupports movably mounted on the bridge deck. The ends of the platformare alternately suspended from horizontally retractable supportsintermediate the pair of supports. Movement of the platform is permittedby retracting each support as necessary to clear obstructions and'thenmoving all supports as a unit along the bridge deck until a subsequentobstruction is again encountered. By alternately supporting the plafiormfrom the various supports and retracting those supports not in use tosuspend the platform one can work the platform across the completelength of a bridge, holding the platform at any desired position alongthe bridge as required for manual work at the underside of the bridgedeck.

It is one object of this invention to provide a scaffold tender capableof meeting the requirements of contractors and governmental agenciesconcerned with the safety of men working along the undersides of abridge deck, while providing for longitudinal movement of the scaffoldtender through upright members and obstructions at the sides of thebridge deck. Another object of this invention is to provide such ascaffold tender which is adaptable to any highway bridge.

LII

These and further objects will be evident from the following disclosureof a preferred embodiment of the invention. Modifications can obviouslybe-made in the illustrated embodiment without deviating. from the basicconcepts and objects of the invention.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational :sectional view ofa preferred 'einbodiment of the invention, taken transversely through atypical bridge deck structure tothecenterline'of the bridge and thescaflold tender supported thereon;

FIG. 2 is a top view of the structure shown in FIG. 1;

FIG. 3 is a side elevational view of the structure shown in FIG. 1;

'FIG. 4 is an enlarged fragmentary sectional view taken along line 4-4in FIG. 1;

FIG. 5 is an enlarged fragmemtarysectional view taken along line 4-5 inFIG. 2;

FIG. 6 is an enlarge fragmentary sectional view taken along line 6 -6 inFIG. 2; FIGS. 7-12 illustrate'thesteps by which the scafiold tender ismoved along the bridge through fixed abutments;

FIG. 7 is a schematic-top view of the scaffold tender in a stationaryworking position;

FIG. 8 is a side elevation view corresponding to FIG. 7;

FIG. 9 is a top view showing retraction of one support which has clearedone of the vertical abutments;

FIG. 10 is a side elevation view corresponding to FIG. 9;

FIG. 1 1 is a schematic top view showing the repositioning of thesupports after clearing the abutment; and

FIG. 12 is a side elevation view corresponding to FIG. 11.

including a concrete bridge deck 10, curb 11 and side rail 12.

For ease of illustration, the bridge structure is illustrated only tothe longitudinal centerline, it being understood that the bridgestructure and the scaffold apparatus are each symmetrical about thiscenterline.

The bridge deck 10 is typically supported by upright piers 13, one ofwhich is shown in the background in FIG. I. The concrete deck 10 ispoured along conventional stringers 14 carried by transverse girders 15.The girders 15 are interconnected at each side of the bridge by a lowertruss chord which in turn is suspended by upright truss members 17 whichare conventionally connected across their upper ends by an upper trusschord (not shown). In other types of bridge construction, the trussmembers 17 are replaced by cables which suspend the bridge between thepiers at each end of an open span. In either instance, uprightobstructions are located in a varying spatial arrangement along the spanof the bridge deck 10. The problem solved by this disclosure is thedifiiculty involved in suspending scaffolding across the underside ofthe bridge deck by overhanging members which project through the uprightobstruction, while providing pratical means by which the supports can beworked across the bridge without dismantling the scaffold tender or thescafiolding supported thereby.

The scaffold tender comprises a framework made in two separatecomponents. As shown, there is a rectangular side unit 18 at eachtransverse side of the scaffold tender. If desired, a rigid frame (notshown) may be bolted between the two side units 18 to form an integralrigid framework that extends substantially across the entire width ofthe bridge deck 10. when spaced as shown, units 18 provide centralclearance on deck 10 for traffic or construction purposes. Each sideunit 18 of this framework is supported by two sets of wheels 21, 22.

ty support the framework and relieve the weight on the wheels 21, 22while holding the framework in a stationary position relative to thebridge deck 10. The general structure of the wheel assemblies and jacks23 is conventional and further detail is not believed necessary to anunderstanding of the present invention.

Mounted at each side of the framework at an elevation above the curb 11and rail 12 are a plurality of outwardly extensible supports. Thesesupports include a pair of horizontal beams 25, 26 and an inter-mediatebeam 27. The beams 25, 26 and 27 are longitudinally spaced from oneanother. They are mounted in a common horizontal plane and are parallelto one another. Each is movably mounted to the side unit 18 of theframework for movement between an extended position shown in FIGS. 1, 2and 3 wherein the support protrudes outwardly beyond the uprightabutrnents provided by the truss members 17, and a retracted positionwherein the supports are entirely within the boundaries of the bridgedeck 10.

The beams 25 and 26 are illustrated as being l-beams movably supportedbetween transverse channels 28 which are fixed across the top of eachside unit 18 at the respective front and rear ends thereof. Transverselyspaced sets of rollers 30 are journaled on the channels 28 (FIG. 4). Theoutside set of rollers 30 engagethe upper flange of each beam 25, whilethe inside set of rollers 30 engage the lower flanges to counteractthe'forces exerted on the beam when in its extended position. Tofacilitate inward movement of the beams 25, 26 parallel to their length,small rollers31 are provided between the channels 28. The lower beamsurfaces ride along the rollers 31 during beam movement, but clear therollers 31 when the beams are fully extended.

The wider intermediate beam 27 at each side of the scafiold tender isconstructed of two spaced channels mounted back to back and separated bya connecting truss structure. Beam 27 is similarly supported by two setsof rollers 32 (FIG. and by rollers corresponding to the previouslydiscussed rollers 31.

The suspended scaffold is shown generally in FIGS. 1, 2 and 3. Itcomprises a pair of scaffold slings 33 at each side of the bridge. Eachend of each sling 33 is suspended by a cable 34 and bridle 35. The upperend of the cables 34 can be selectively anchored to the outer ends ofthe beams 25, 26 or 27, as will be described below. Extending across theunderside of the bridge deck and carried by the slings 33 are transverseplanks 36 or other types of transverse work platforms. These platformsprovide manual access under the bridge deck for purposes of strippingconcrete forms from the underside of the deck or for painting the bridgestructure, making repairs, inspections, etc.

The present method supporting the transverse working platform beneathbridge deck 10 involves the step of projecting one or more beams 25, 26or 27 through the upright obstructions, such as the truss members 17,and suitably suspending the slings 33 and cables 34 so as to maintainthe planks 36 in a stable working condition. During use of the workingplatform, the framework should be fixed relative to the bridge deck by Ithe jacks 23 or other equivalent locking arrangements provided to holdthe framework stationary relative to the deck 10. When working atconsiderable height, individual safety harnesses (not shown) can beutilized by workmen on the planks 36.

When it is necessary to move the working platform afforded by planks 36,those persons carrying out operations on the underside of the deck aretransferred to the bridge deck 10 by a ladder or other suitable liftingdevice (not shown). The slings 33 are then alternately suspended bycables 34 from one or more of the beams 25, 26 or 27 which are free tomove longitudinally along the bridge deck 10 without abutting a trussmember 17. Those beams 25, 26 or 27 in immediate abutting positionrelative to a truss member 17 are manually retracted or moved inwardrelative to the bridge deck 10. The framework can then be moved alongthe bridge deck 10 by attachment to a tractor or other vehicle (notshown) until the retracted beam has cleared the abutment. It can then beagain extended and cable 34 reconnected as desired. By providingalternate suspension of the cables 34 from both outer beams 25, 26, oneouter beam 25 or 26 and the intermediate beam 27, or from the widerintermediate beam 27, and selectively retracting and extending the beams25, 26 and 27 as necessary to work through the upright truss members 17,the scaffold tender can be moved in small steps across the entire lengthof the bridge deck 10. A winch assembly 38 on each framework side unit18 is used to move the units in conjunction with a fixed anchor (notshown) and is alternately used to lift sling 33 during weight transfer.

The general steps by which the scaffold tender is moved are shown inFIGS. 7-12. In FIGS. 7 and 8, beams 25 are in immediate abuttingposition adjacent to a truss member. Cables 34 are suspended from theouter beams 25, 26 in a working condition. The scaffold tender would beheld stationary in this position during operations under the bridge deck10. When it is desired to move the working platform, the forward cable34 would be shifted from the beams 25 to the intermediate beams 27. Thiswould be accomplished by connecting a substitute cable 34 between theforward end of each sling 33 and the intermediate beams 27, and thenreleasing the previously used cable 34. The sling 33 would remain in ahorizontal position suspended between the beams 26, 27 in the mannershown in FIG. 10.

After release of cable 34 from the beams 25 they can be retracted asshown in FIG. 9. The framework can then be moved in a forward directionas illustrated by arrow 37.

After the upright truss member 17 has been cleared, the beams 25 canagain be extended as shown in FIG. 11 and cables 34 can be reconnectedbetween sling 33 and the outer ends of beams 25 in the manner shown inFIG. 12. These steps can be repeated as necessary in order to workthrough any conventional pattern of truss members, cables, posts, etc.,which might be encountered at the side of a bridge.

When encountering a pier at the underside of the bridge, it is necessaryto either remove the planks 36 from the slings 33 or connect one end ofeach plank 36 to a single sling 33 and allow the planks to drop from theremaining sling 33.

Should both beams 25, 26 be in abutment with an upright along a bridgewhile encountering upright obstructions having 7 variable spacing alongthe length of the bridge as is conventional in bridge span construction.

The apparatus illustrated is extremely versatile and adaptable to anytype of concrete bridge deck or similar bridge construction. The twoside units 18 are located at the respective sides of the deck and havean effective working width slightly less than the bridge deck width.They are easily transported from one location to another.

Obviously, some modifications can be made with respect to the precisedetails shown in the drawings and discussed above.

What is claimed is:

1. A scafiold tender for movably suspending a transverse workingplatform beneath the deck of a highway bridge of the like, comprising:

a framework having an effective width less than the width of said bridgedeck;

said framework being movably carried by a plurality of wheels inengagement with the upper surface of the bridge deck, whereby theframework can be longitudinally moved along the bridge deck;

means on said framework for selectivity fixing the location of saidframework relative to the bridge deck;

and a plurality of transverse supports mounted to said framework andlongitudinally spaced from one another at both sides of the framework;

each support being independently mounted on said framework for selectivemovement relative to the framework between a retracted position whereinthe entire support located inward of the transverse boundaries of thebridge deck and an extended position wherein one end thereof is locatedoutward of said boundaries; and

means mounted to said one end of each support for releasably supportinga working platform extending transversely beneath the bridge deck.

2. A scaffold tender as set out in claim 1 wherein the longitudinalspacing between supports at each side of said framework is such as topermit longitudinal movement of the framework along the bridge deckwhile at least one of said supports is in its extended positions andreceived between truss members at the sides of the bridge deck.

3. A scaflold tender as set out in claim 1 wherein each support while inits extended position, is cantilevered on said framework in a horizontaltransverse position.

4. A scaflold tender as set out in claim 1 wherein each support, whilein its extended position, is cantilevered on said framework in ahorizontal transverse position;

each support being movably guided on said framework for transversetranslational movement in a direction parallel to the length of thesupport between its retracted and extended positions.

5. A seaflold tender as set out in claim 4 wherein each of said supportsis provided with a releasable locking element operatively connectedbetween it and said framework for selectivity securing the supportrelative to said framework in either its retracted or extended position.

6. A scafiold tender as set out in claim 1 wherein said frameworkcomprises:

a pair of identical side frames having said supports mounted thereto;

said frames being symmetrically arranged at the respective sides of thebridge deck.

7. A scaffold tender as set out in claim 1 wherein each supportcomprises a horizontal beam movably mounted to the framework fortranslational motion parallel to the length of said support, saidsupports being parallel to one another.

8. A method of supporting a transverse working platform beneath the deckof a highway bridge of the like, comprising:

suspending the respective ends of the platform from a pair oflongitudinally spaced and horizontally retractable supports mounted onthe bridge deck; alternately suspending the ends of the platform fromhorizontally retractable supports intermediate the pair of pp retractingeach support transversely relative to the bridge deck as necessary toclear obstructions at the side of the bridge deck; and

moving all supports as a unit along the bridge deck.

1. A scaffold tender for movably suspending a transverse workingplatform beneath the deck of a highway bridge or the like, comprising: aframework having an effective width less than the width of said bridgedeck; said framework being movably carried by a plurality of wheels inengagement with the upper surface of the bridge deck, whereby theframework can be longitudinally moved along the bridge deck; means onsaid framework for selectivity fixing the location of said frameworkrelative to the bridge deck; and a plurality of transverse supportsmounted to said framework and longitudinally spaced from one another atboth sides of the framework; each support being independently mounted onsaid framework for selective movement relative to the framework betweena retracted position wherein the entire support located inward of thetransverse boundaries of the bridge deck and an extended positionwherein one end thereof is located outward of said boundaries; and meansmounted to said one end of each support for releasably supporting aworking platform extending transversely beneath the bridge deck.
 2. Ascaffold tender as set out in claim 1 wherein the longitudinal spacingbetween supports at each side of said framework is such as to permitlongitudinal movement of the framework along the bridge deck while atleast one of said supports is in its extended positions and receivedbetween truss members at the sides of the bridge deck.
 3. A scaffoldtender as set out in claim 1 wherein each support while in its extendedposition, is cantilevered on said framework in a horizontal transverseposition.
 4. A scaffold tender as set out in claim 1 wherein eachsupport, while in its extended position, is cantilevered on saidframework in a horizontal transverse position; each support beingmovably guided on said framework for transverse translational movementin a direction parallel to the length of the support between itsretracted and extended positions.
 5. A scaffold tender as set out inclaim 4 wherein each of said supports is provided with a releasablelocking element operatively connected between it and said framework forselectivity securing the support relative to said framework in eitherits retracted or extended position.
 6. A scaffold tender as set out inclaim 1 wherein said framework comprises: a pair of identical sideframes having said supports mounted thereto; said frames beingsymmetrically arranged at the respective sides of the bridge deck.
 7. Ascaffold tender as set out in claim 1 wherein each support comprises ahorizontal beam movably mounted to the framework for translationalmotion parallel to the length of said support, said supports beingparallel to one another.
 8. A method of supporting a transverse workingplatform beneath the deck of a highway bridge of the like, comprising:suspending the respective ends of the platform from a pair oflongitudinally spaced and horizontally retractable supports mounted onthe bridge deck; alternately suspending the ends of the platform fromhorizontally retractable supports inTermediate the pair of supports;retracting each support transversely relative to the bridge deck asnecessary to clear obstructions at the side of the bridge deck; andmoving all supports as a unit along the bridge deck.